1. Field of the Invention
The invention relates to a security arrangement for motor vehicle equipped with a, main or access, programmed monitoring system, and in particular with a so-called xe2x80x9chands-freexe2x80x9d monitoring system.
2. Description of Related Art
In a vehicle equipped with such an access monitoring system, a number of operations which required the use of a key, and, in particular, the opening of the doors of the vehicle, the enabling of the antitheft system and the starting of the engine, are initiated after an exchange of data over the airwaves between a recognition device with which the vehicle is equipped and a designated identifying device carried by the user, when the latter enters the zone of range intended for the initiating of these operations.
These operations are carried out in a general way by electrical control, when a xe2x80x9chands-freexe2x80x9d system is employed and it is essential to eliminate any risk of inadvertent initiation of an operation during a phase of functioning where it is not intended. Such inadvertent initiation may, for example, occur because of a failure arising at the level of one of the components of the monitoring system and for example because of a fault attributable to incorrect functioning of a processor. It is thus particularly important to eliminate the risk of a locking of a vehicle antitheft system, while the vehicle is moving, or the risk of a cutoff of the current supplying safety systems, such as the injection management system, the wheel antilock system, or the vehicle balance monitoring system, following a failure occurring at the level of a component of some other system and in particular of the xe2x80x9chands-freexe2x80x9d monitoring system.
It is clear that the risk of inadvertent initiation of an operation exists in other working cases and in particular from the moment a fault caused by incorrect functioning of a monitoring system, main or higher level, is liable to affect the functioning of other systems of the vehicle, which depend thereon in one way or another.
Now, one drawback inherent in a programmed monitoring system, for example in a system comprising a microprocessor, is the inability to obtain a sufficiently reliable indication regarding the failure rate of the system on account of its mixed hardware/software construction.
The invention therefore proposes a security arrangement for motor vehicle equipped with a programmed monitoring system and with at least one specific system to which it transmits commands, which arrangement comprises hard-wired logic mounted between a control facility and the specific system, as is the monitoring system, so as to block the command transmitted by this monitoring system to the specific system, when this command corresponds to that which is obtained in respect of an instruction received by the control facility and when such an instruction has not been received from the control facility by the hard-wired logic.
The decision to choose hard-wired logic in order to reduce the risks is motivated by the fact that the failure rate of such logic is always less than that which it is possible to obtain with the aid of an elaborate programmed system, when a relatively simple operation is to be carried out.
Advantageously, the control facility is made available to a user so as to allow him to transmit specific instructions to the vehicle.
More generally, the control facility is designed to receive instructions originating from various systems for managing specific functions of the vehicle functioning upstream of the security arrangement according to the invention.
In one embodiment of security arrangement for vehicle equipped with an antitheft specific system, the hard-wired logic receives, on the one hand, a turn-off instruction, which is delivered to the monitoring system by means of the control facility, and which brings about the delivery of a locking command by the monitoring system destined for the antitheft system, on the other hand, an indication of the state of functioning of the vehicle which manifests the presence of the supply current distributed within the vehicle from the turn-on phase, until turn-off, the said logic blocking any locking command sent by the monitoring system, if the supply current is distributed and if said logic has not itself received the turn-off instruction.
In one embodiment of a security arrangement for vehicle equipped with a specific system monitoring the supply of current to the vehicle while it is functioning, the hard-wired logic receives a vehicle engine turn-off instruction which is delivered to the monitoring system by means of the control facility, and which brings about the delivery of a supply cutoff command by the monitoring system destined for the specific system. Moreover the hard-wired logic comprises clock means which allow it to deliver a security signal corresponding to a time window of specified duration, on receipt of a turn-off instruction, so as to block at the level of a logic circuit, of AND type, any supply cutoff command transmitted by the monitoring system destined for the specific system, via the logic circuit, when this command is outside the said time window.
The invention also relates to a security arrangement for vehicle comprising a so-called xe2x80x9chands-freexe2x80x9d monitoring system and a vehicle comprising at least one security arrangement defined hereinabove.